| 1. |
- Bergkvist, Bo, et al.
(författare)
-
Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden
- 2008
-
Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 89:1, s. 7-25
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured 2001-2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold, respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from fine roots (< 1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference in total litter input rate between the sites almost disappeared (190-233 g C m(-2) year(-1)). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging from -8 g C m(-2) year(-1) in the north to +9 g C m(-2) year(-1) in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m(-2) year(-1).
|
|
| 2. |
|
|
| 3. |
- Dahlberg, Leif, et al.
(författare)
-
Starkt samband övervikt/obesitas och ortopediska åkommor. Fetmaepidemins konsekvenser vidgas.
- 2008
-
Ingår i: Läkartidningen. - 0023-7205. ; 105:34, s. 2246-2248
-
Tidskriftsartikel (refereegranskat)abstract
- t is well known that overweight/obesity are risk factors for several important conditions of internal medicine. The positive correlation between gonarthrosis and a high BMI is also well investigated. However, the possible correlation between owerweight/obesitas and other orthopaedic conditions are less well studied and are therefore rarely discussed in either medical terms or economical considerations. Objective: To examine the relationship between owerweight/obesity and orthopaedic conditions. Patient BMI was compared with a reference population BMI in two assessments. In one we investigated patients who were diagnosed with ankle fracture in the emergency room (n=79). In the other we investigated outpatients with various orthopaedic conditions (n=647). In both assessments patients were recruited in a consecutive mode. The BMI of the patients with ankle fracture was self reported as were the BMI of the normal population. The outpatients were weighted and measured. Patients with ankle fractures differed significantly from the reference population, (1.92 units (p<0.001). The fracture odds ratio of BMI>30 was 3.46 (p<0.001). Similarly, the outpatients had 1.44 higher BMI units than the references (p<0,001). Odds ratio to become an orthopaedic outpatient if BMI>30 was 2.3 (p<0.001). In both investigations results were age and gender standardised. Both studies indicate that there is a positive correlation between BMI and the risk of sustaining orthopaedic conditions. Although there may be reporting-bias, results seem prominent enough to conclude that orthopaedic conditions may be added to other medical disciplines regarding negative consequences of overweight/obesity and strengthens the need for preventive measures aimed at the epidemic progress of overweight/obesity.
|
|
| 4. |
- Åkerblom, Staffan, et al.
(författare)
-
Partitioning of Hg between solid and dissolved organic matter in the humus layer of boreal forests
- 2008
-
Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 1573-2932 .- 0049-6979. ; 189:1-4, s. 239-252
-
Tidskriftsartikel (refereegranskat)abstract
- The mobility of mercury (Hg) deposited on soils controls the concentration and toxicity of Hg within soils and in nearby streams and lakes, but has rarely been quantified under field conditions. We studied the in situ partitioning of Hg in the organic top layer (mor) of podsols at two boreal forest sites differing in Hg deposition and climatic regime (S. and N. Sweden, with pollution declining to the north). Soil solution leaching from the mor layer was repeatedly sampled using zero-tension lysimeters over 2 years, partly in parallel with tension lysimeters. Concentrations of Hg and dissolved organic carbon (DOC) were higher while pH was lower at the southern site (means +/- SD: Hg=44 +/- 15 ng L-1, DOC=63.0 +/- 31.3 mg L-1, pH=4.05 +/- 0.53) than at the northern site (Hg=22 +/- 6 ng L-1, DOC=41.8 +/- 12.1 mg L-1, pH=4.28 +/- 0.43). There was a positive correlation over time between dissolved Hg and DOC at both sites, even though the DOC concentration peaked during autumn at both sites, while the Hg concentration remained more constant. This correlation is consistent with the expected strong association of Hg with organic matter and supports the use of Hg/C ratios in assessments of Hg mobility. In the solid phase of the overlying O-f layer, both Hg concentrations and Hg/C ratios were higher at the southern site (means +/- SD: 0.34 +/- 0.06 mu g g(-1) dw and 0.76 +/- 0.14 mu g g(-1) C, respectively) than at the northern site (0.31 +/- 0.05 mu g g(-1) dw and 0.70 +/- 0.12 mu g g(-1) C, respectively). However, concentrations in the solid phase differed less than might be expected from the difference in current atmospheric input, suggesting that the fraction of natural Hg is still substantial. At both sites, Hg/C ratios in the upper half of the mor layer were only about two thirds of those in the lower half, suggesting that the recent decrease in anthropogenic Hg deposition onto the soil is offset by a natural downward enrichment of Hg due to soil decomposition or other processes. Most interestingly, comparison with soil leachate showed that the average Hg/C ratios in the dissolved phase of the mor layers at both sites did not differ from the average Hg/C ratios in the overlying solid organic matter. These results indicate a simple mobilisation with negligible fractionation, despite differences in Hg deposition patterns, soil chemistry and climatic regimes. Such a straight-forward linkage between Hg and organic matter greatly facilitates the parameterisation of watershed models for assessing the biogeochemical fate, toxic effect and critical level of atmospheric Hg input to forest soils.
|
|
